The win by the Cubs (89-62), combined with the Reds’ win over the Brewers (86-66), expanded the Cubs lead to 3½ games in the National League Central while reducing their magic number for winning their third consecutive division title to eight.

The eight-run lead after 5½ innings enabled manager Joe Maddon to pull several of his regular position players as the Cubs complete a stretch of 30 consecutive days with a scheduled game Wednesday night.

Baez cranked a 2-0 pitch off Matt Andriese that landed to the right of the 413-foot sign near the swimming pool in right center with two out in the first.

Baez’s homer, his 33rd, followed a 17-pitch at-bat from Anthony Rizzo, who fouled off 11 pitches after falling behind 0-2 before lining out to second.

Daniel Murphy, who led off the game with a single, ripped a two-run home run with two out in the second to cap a three-run rally.

Photos from the Cubs' 9-1 win against the Diamondbacks on Sept. 18, 2018, at Chase Field in Phoenix.

Jason Heyward, making his first start since suffering a right hamstring strain on Aug. 30, ripped a double to left center in his first at-bat and scored on an opposite field double to left by Ian Happ.

Rizzo and Baez hit consecutive RBI singles during a four-run fifth.

Montgomery allowed a solo home run to Ketel Marte in the second but didn’t allow a runner past second after that.

Montgomery pitched six innings for the eighth time and for the first time since returning from the 10-day disabled list on Aug. 30. Montgomery struck out eight and walked one.

Alec Mills helped preserve much of the bullpen by pitching two scoreless innings.